Halogen filament lamp for vehicle headlight with screen partially surrounding antiglare filament

ABSTRACT

A halogen filament lamp for vehicle headlights in which a screen partially surrounds the antiglare filament within the lamp bulb to prevent blinding of a driver of an oncoming car. This screen has a reflecting surface that both blocks certain light rays and reflects same to the parabolic reflector.

United States Patent Riinders [54] HALOGEN FILAMENT LAMP FOR VEHICLE HEADLIGHT WITH SCREEN PARTIALLY SURROUNDING ANTIGLARE FILAMENT [72] Inventor: Johannes Riinders, Emmasingel, Eindhoven, Netherlands [73] Assignec: U.S. Philips Corporation, New York, N.Y.

[22] Filed: June 9, 1969 211 Appl. No.: 831,358

[30] Foreign Application Priority Data June 8, 1968 Netherlands ..6808l09 [52] U.S.Cl. ..3l3/ll5,313/ll7 [51] Int.Cl. ..HOIk9/08 [58] FieldofSearch ..3l3/ll3,ll4,ll5,ll6,l17

[ 1 Feb. 29, 1972 [56] References Cited UNITED STATES PATENTS 3,293,475 12/1966 Grunning et al. ..3 13/] I7 3,5l8,478 6/1970 Bardin .3l3/l 17 2,071,979 2/1937 Honing et a]. ...3l3/l 17 2,617,062 I 1/1952 Rijnders .3l3/l l5 X 3,200,282 8/1965 Mickley.... ..3l3/l l4 3,206,595 9/1965 Lollert ..3l3/l 13 X 3,493,806 2/1970 Jacobs et al. ..3 l3/l 13 Primary Examiner-Robert Segal Attorney-Frank R. Trifari [5 7] ABSTRACT A halogen filament lamp for vehicle headlights in which a screen partially surrounds the antiglare filament within the lamp bulb to prevent blinding of a driver of an oncoming car. This screen has a reflecting surface that both blocks certain light rays and reflects same to the parabolic reflector.

4 Claims, 3 Drawing Figures PATENTEDFEBZSIQYZ 3,646,386

SHEET 1 OF 2 INVENTOR.

JOHANNES RU NDERS M AGENT INVENTOR.

JOHANNES RIJNDERS BY Zytw. 34%

AGEN

HALOGEN FILAMENT LAMP FOR VEHICLE HEADLIGHT WITH SCREEN PARTIALLY SURROUNDING ANTIGLARE FILAMENT The invention relates to a halogen filament lamp for a vehicle headlight lamp comprising a tubular lamp vessel having a driving-light filament and an antiglare filament. The antiglare filament is arranged with its longitudinal axis in the longitudinal direction of the lamp vessel but eccentric with respect to the lamp axis. Viewed in a plane at right angles to the longitudinal axis, the lamp vessel is surrounded by a light intercepting screen which extends in the axial direction of the lamp over an angle of 165 to 180. Such a halogen filament lamp is known and is disposed in a parabolic headlight reflector in such manner that the lamp axis coincides substantially with the axis of the reflector. The screen ensures that the light from the antiglare filament impinges only upon that reflector half so that, assuming that the reflector axis is arranged horizontally, it is directed downwards and thus will not blind the driver of an oncoming car.

As compared with nonhalogen filament lamps, halogen lamps have the advantage of a considerably larger luminous efficiency with a given absorbed power and a given life. As a result of the higher luminous efficiency of halogen filament lamps, it becomes important that the antiglare light should be nonblinding, and it is highly desirable to obtain a prescribed sharp cutting-off of the antiglare beam.

Due to the high intensity of the irradiated light of a halogen filament lamp with respect to a nonhalogen filament lamp, reflections by the wall of the envelope itself play an important part and it is of importance to reduce the consequences of these reflections strongly. In the known halogen filament lamp the antiglare filament is therefore arranged with its longitudinal axis parallel to but eccentrical with respect to the axis of the envelope and at a distance from the axis of the envelope which is at least equal to half the diameter of said filament. As a result of this there is considerable reduction of images of the antiglare filament being reflected on the wall of the envelope and directed upwards in an annoying manner by the reflector.

In the known halogen filament lamp the screen is constituted as a lightabsorbing thin layer of paint on a part of the outside of the envelope of the lamp. Alternatively the screen may be a separate structural component which engages the relative part of the outer wall.

Due to the presence of the light intercepting screen on the outside of the envelope of the lamp, however, a large amount of the antiglare light is lost. It is the object of the invention to mitigate this drawback and to obtain thus a considerable increase of the light output in the antiglare beam.

The halogen filament lamp according to the invention has on its side facing the antiglare filament a screen comprising a direct reflecting surface that has one part positioned between the antiglare filament and the wall of the tubular part of the lamp vessel, and another part extending between the two filaments. The part of the screen situated between the end faces of the two filaments facing each other extends at right angles to the lamp axis and has a shape such that rays from the antiglare filament reflected by said part of the screen, are reflected at an angle of at most 60 with the lamps axis in a direction remote from the driving-light filament; the remaining part of the screen has a shape such that rays from the antiglare filament reflected by said remaining part of the screen do not pass a region situated concentrically inside the tubular lamp vessel and which is situated between the end faces and has a radius of maximally 2.5x the diameter of the antiglare filament. A large part of the light from the antiglare filament intercepted by the screen is reflected and received on the upper half of the reflector. By giving the screen a prescribed shape as described above, the light rays from the antiglare filament which impinge upon the upper half of the reflector of the above mentioned headlight, do not cause blinding. The focus of the reflector is situated in or in the immediate proximity of the region bounded between the end faces. It has been found experimentally that for the rays reflected by the part of the screen present between the adjacent end faces of the two filaments, the angle in question with the lamp axis should not exceed 60".

It is to be noted that it is known per se in nonhalogen lamps which show a considerably lower luminous efficiency than halogen filament lamps, to arrange an antiglare cap in the lamp vessel, said cap comprising a cup-shaped dull blackened part extending from a place between the filament which part adjoins a more or less cylindrical curved readily reflecting mirror part which partly surrounds the antiglare filament. With the low brightness of this type of filament, said dull blackened part results in only weak reflection which, is hardly annoying. The use of such a dull blackened layer on the screen in a halogen filament lamp with much larger brightness is hardly possible on the one hand already due to the chemical action of the filling gas. On the other hand, such a blackened layer in a halogen filament lamp would have a larger light reflecting effect, and thus cause clearly noticeable annoying reflections on the upper half of the reflector to be used in said halogen filament lamp, the focus of which is situated in or in the very immediate proximity of the region between the said end faces of the two filaments facing each other. The end in view in the known lamp was not that the blackened surface can be replaced by a direct reflecting surface to increase the luminous efficiency in the antiglare beam, when the shape of the reflecting screen is only suitably chosen.

A preferred embodiment of the halogen filament lamp according to the invention is characterized in that the screen comprises a segment of a hollow cylinder which surrounds the antiglare filament over preferably half its length remote from the driving-light filament; the axis'of the envelope is situated between the cylinder axis and the longitudinal axis of the antiglare filament and parallel to said axes, a curved part of the screen extends between the two filaments adjoining said cylinder segment, the centers of curvature of the radius or raddi of curvature of said part being situated on the axis of the cylindrical part.

In order that the invention may be readily carried into effect, one embodiment thereof will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which FIG. 1 shows a parabolic automobile headlight reflector with halogen filament lamp arranged therein according to the invention.

FIG. 2 is a cross-sectional view taken on the line Il-II of 1 FIG. 1.

FIG. 3 serves to illustrate the effect of the directed reflecting screen.

In the diagrammatic FIG. 1, reference numeral 1 denotes the tubular part of the halogen filament lamp which cooperates with a parabolic reflector 3 as an automobile headlight. The focus is denoted by F. A driving-light (main) filament 5 and an antiglare auxiliary filament 7 are eccentrically arranged in the lamp in the conventional manner.

Substantially all the rays directed downwards by the antiglare filament of this lamp are intercepted by a screen 9, so that the reflector's lower part 11 situated outside the central part can not receive any antiglare light. So when the antiglare light is in operation substantially no glaring can occur via radiation directed upwards by reflector part 11.

The screen antiglare 9 is formed as a cap which surrounds the antiglare filament 7 (see also FIG. 2) over an angle of to On the side facing the antiglare filament 7, the cap shows a direct reflecting mirror surface which reflects the antiglare light for a considerable part to the upper reflector part 15, and thus contributes to an antiglare light beam having a light intensity which is greater than would be obtained with a screen which is absorbing, for example, dull black, throughout its inner surface.

The screen 9 comprises three adjoining parts b, c and d, each having a particular shape.

For example, the part b is shaped as a segment of a hollow cylinder, the axis 13 of which extends parallel to the axis 17 of the envelope. Two other parts c and d adjoin part b and together constitute a spherical segment, the radius of which has a center which is situated just on the right of the center M of the antiglare filament 7 on the axis 13.

Reference numeral 19 in F IG. 3 denotes the most unfavorable light ray. Due to the shape of the part b, the reflected ray 20 crosses the antiglare filament 7 and does not pass the region a where the focus F is situated. This ray 20, after reflection on the reflector part 15, will be directed downwards, and hence produce no glare to the driver of an oncoming car.

Reference numeral 21 denotes another unfavorable light ray which is reflected by the part c of the screen and crosses the antiglare filament in a direction according to the ray 23, and is also directed downwards after reflection on the part 15 of the reflector.

Reference numeral 25 denotes still another unfavorable light ray which is reflected by the part d of the screen in a direction denoted by 27 according to an angle of 60 with the axis 13 of the screen 9.

It is thus found that optimum results are obtained when it is ensured that light rays from the antiglare filament 7 reflected by the parts b and c of the screen, do not pass the shaded area in FIG. l. [t has been found experimentally that this area is coaxial with the tubular part of the lamp vessel, extends over the distance a in FIG. 1 and comprises a radius R which is at most 2.5x the diameter of the antiglare filament.

It has also been found experimentally that the best results are obtained when rays from the antiglare filament 7 reflected by the part d cannot impinge upon the upper half 15 of the reflector which can be achieved when the angle between a reflected ray 27 and the lamp axis is maximally 60.

What is claimed is:

l. A halogen filament lamp including a. a tubular bulb having a central, longitudinal axis, and which when orientated horizontally has upper, lower front and rear parts,

b. a main filament, and

c. an antiglare filament axially spaced and secured in the rear and front parts respectively of the bulb, the antiglare filament having a central longitudinal axis disposed generally parallel to and below the axis of the bulb, and a screen comprising (i) a first part formed as segment of a cylindrical tube having a central axis generally parallel to that of the bulb and corresponding front and rear parts, the screen at least partially surrounding the lower and front parts of the antiglare filament as viewed in front elevation view, extending upward on both sides defining an arc of from and (ii) a second part formed as a segment of a sphere extending from the rear of the first screen part into the region between the two filaments, the surface of the screen facing the antiglare filament being direct reflecting thereby blocking light from the antiglare filament from reaching at least portions of said region, with at least some of said blocked rays being reflective off said surface.

2. A lamp as claimed in claim 1, wherein said blocked region has a diameter maximally 2.5 times that of the antiglare filament.

3. A lamp as claimed in claim 1, wherein the radii of curvature of the first and second parts of the screen are the same.

4. A lamp as claimed in claim 1, wherein the rearmost portion of the curved part of the screen reflects light rays from the antiglare filament at angles having a maximum of 60 with respect to the bulbs axis. 

1. A halogen filament lamp including a. a tubular bulb having a central, longitudinal axis, and which when orientated horizontally has upper, lower front and rear parts, b. a main filament, and c. an antiglare filament axially spaced and secured in the rear and front parts respectively of the bulb, the antiglare filament having a central longitudinal axis disposed generally parallel to and below the axis of the bulb, and a screen comprising (i) a first part formed as segment of a cylindrical tube having a central axis generally parallel to that of the bulb and corresponding front and reaR parts, the screen at least partially surrounding the lower and front parts of the antiglare filament as viewed in front elevation view, extending upward on both sides defining an arc of from 165* - 180*, and (ii) a second part formed as a segment of a sphere extending from the rear of the first screen part into the region between the two filaments, the surface of the screen facing the antiglare filament being direct reflecting thereby blocking light from the antiglare filament from reaching at least portions of said region, with at least some of said blocked rays being reflective off said surface.
 2. A lamp as claimed in claim 1, wherein said blocked region has a diameter maximally 2.5 times that of the antiglare filament.
 3. A lamp as claimed in claim 1, wherein the radii of curvature of the first and second parts of the screen are the same.
 4. A lamp as claimed in claim 1, wherein the rearmost portion of the curved part of the screen reflects light rays from the antiglare filament at angles having a maximum of 60* with respect to the bulb''s axis. 